The present invention relates to the field of identification bar codes, readers, and scanners, and more particularly, is directed to a bar code stencil and method of using such a stencil to integrally embed, bond, attach, mold, or adhere a bar code into or onto an article during its manufacture, remanufacture, rebuilding, or revitalization. The stencil may also be used in a postproduction or aftermarket refit identification procedure for bar code marking of articles.
The development of modern bar codes began in the 1940s in response to the food industry""s need for a reliable and economical system for inventory control and for automatically reading product information at grocery store checkouts. The first patent to issue on such a system is believed to be U.S. Pat. No. 2,612,994 entitled Classifying Apparatus and Method and which issued on Oct. 7, 1952.
Although the coding system used in the ""994 patent relied on a series of concentric circles to encode the identification information, the original coding approach developed by the inventors was a series of narrow and wide vertical lines much like present day bar code systems. Early implementations of the concentric circle approach proved unreliable however, as the circles were difficult to print without smearing. Smeared circles introduced reading errors when scanned and thus were unacceptable. The use of vertical bars eliminated the smearing problem and associated scanning errors.
Since the adoption of the Universal Product Code (UPC) in 1973, bar codes have proliferated to virtually all areas of article and product identification. Bar codes are now widely recognized as an economical and reliable identification system.
Over the years, a number of different versions of the UPC bar code have been developed. Version A is one of the most popular and is illustrated in FIG. 1. The Version A format includes a plurality of spaced vertical bars 1 which form the bar code and a plurality of human readable digits which correspond to the bar code, i.e., xe2x80x9c0 25528 43507 3xe2x80x9d as indicted by reference number 2.
As shown in FIG. 1, the code is divided into 12 digits, with the first digit 3 being usually a xe2x80x9c0xe2x80x9d. The next five digits 4 are assigned to the product manufacturer by the Uniform Code Council and thus serve to identify the manufacturer. Accordingly, all of the bar codes for the same manufacturer will have these same five digits. The next five digits 5 represent the item identification code given to a particular product by the manufacture. Thus, 99,999 products can be uniquely identified. The final twelfth digit 6 is a check digit which is used by the bar code scanner to confirm the accuracy of the scan.
Each of the human readable digits is encoded into the code using a two-part binary coding system as indicated in the table below:
Each A1xe2x80x3 in the key code is represented by a black bar 7 as illustrated in FIG. 1 and each A0xe2x80x3 in the key code is represented by a white line or space 8. There is a center code of four lines (binary digits 01010) which bisect the bar code. On the left side of the bar code, the Left Binary Code digits from the above table are used and on the right side of the bar code, the Right Binary Code digits from the table are used. This mirror image coding technique allows the scanner to read the number code in either direction. Start and stop codes are used by the scanner to set the width of the binary digits within the bar code symbol. The scanner also uses the check digit to calculate a check sum as is know in the art. If the correct check sum is not calculated, the bar code read is rejected.
FIG. 2 is a further illustration of a typical UPC bar code with its constituent parts labeled.
As a testament to the popularity of bar code use, the UPC bar code is scheduled to be phased out by the year 2005 because its 12-digit length will no longer be sufficient to handle the demand for bar codes. In its place, the United States is expected to adopt a version of the European Article Numbering (EAN) system. The EAN bar code system has thirteen digits and can thus accommodate substantially more product identifications than the UPC.
The traditional printed bar code system continues to serve its original purpose of grocery store inventory control and check out very well. Bar codes formed of conventional two-dimensional printed bars work well where the article to be labeled is not subject to a harsh environment and the bar code label is not likely to be rubbed off or smeared over so that it cannot be read.
The food industry serves as an ideal environment for conventional bar codes. Bar codes used for food labeling are unlikely to be subjected to harsh environments due to the inherent need to prevent adulteration and damage to the food package. Thus, the bar code label is not likely to become damaged or unreadable.
The bar code system has in some respects however, become the victim of its own success. Today, attempts are being made to use bar codes in many environments in which a conventional printed two-dimensional bar code, such as the one used for food products, cannot be used. One such environment is the tire manufacturing industry.
U.S. Pat. No. 5,160,383 assigned to Goodyear Tire and Rubber discloses one example of the use of a bar code labeling technique in the tire industry. According to the patent, it is important that a tire label be highly durable so that it may still be read after many years of tire service and multiple retreadings. The patent also notes that serial numbers can be molded into tire sidewalls but that doing so is labor intensive and costly. Thus, Goodyear sought to improve upon conventional tire labeling systems by attaching an identification label to the rubber inter lining of an uncured tire. The label is made of two materials which are co-curable with the rubber of the tire. The tire is then cured using a conventional curing process which results in the label becoming permanently affixed to the inside of the tire.
Goodyear also is the assignee of U.S. Pat. No. 4,625,101 which discloses a method of molding a bar code configuration onto the sidewall of a tire. The bar code configuration has a plurality of sloped reflective surfaces which allow more flexibility in locating the bar code scanner without adversely effecting the accuracy of the scan. A bar code plate mold insert is used to mold the bar code configuration into the sidewall of the tire during the vulcanization process.
Another technique for labeling a tire is disclosed in U.S. Pat. No. 4,941,522 assigned to the Yokohama Rubber Company. The Yokohama approach involves an improved bar code plate mold insert which is also used to mold a bar code into a side wall of the tire during the vulcanization process. The improved plate is said to solve the problem of deterioration of the tire""s resistance to weather in the area of the molded bar code.
The instant invention differs from the above-cited patents in many respects, the chief of which being both the uniqueness of each stencil and the disposability of the stencil. That is, the instant invention requires that each stencil be made with a code unique to the part being marked. Because harsh environment marks are typically placed on durable goods, i.e., car parts, aerospace parts, heavy equipment parts, oil pipes, etc., the market and regulatory need is for traceability throughout the useful life of the part and the piece of equipment, machine, or item of which the marked part is assembled into. In essence, the marks made possible by the instant invention will allow databases to be developed which follow the marked part from the date of marking to the end of the useful life. It is contemplated that the marks made possible by the instant invention will play an important role in facilitating databases of safety critical parts in many, many industries, including aerospace, automotive, energy, and the like.
Like the tire manufacturing industry, bar code labels also have great utility in other harsh environments as well. For example, domestic metal casters cast and ship millions of tons of product each year. An effective way to identify each product for tracking and inventory control purposes is to label it with a bar code. Because casts usually are subjected to a post casting process to finish and shape them to their final form, a conventional printed bar code label is often difficult to apply to a casting surface and is also subject to being rubbed off or covered over during the subsequent finishing process. Moreover, a printed bar code label is likely to deteriorate over time, well before the end of the life of the cast itself, making the bar code difficult or impossible to read.
Ideally, an identification bar code will be embedded into the article during the manufacturing process. Doing so, avoids the possibility of misidentification, i.e., the wrong bar code being applied, in a subsequent labeling step.
In order to improve the durability and readability of bar codes in harsh environments such as casting, a three-dimensional bar code construction was developed. An end view of a portion of such a bar code is illustrated in FIG. 3. Each bar has a width 30 and a height 31. The distinguishing feature of this type of bar code is its height 31. The bar code is scanned by a three-dimensional bar code reader which detects the presence or absence of a bar based on its height rather than its contrast as a conventional two dimensional bar code reader does. Thus, a three dimensional bar code can be read when no color contrast is available. Contrast, for reading purposes, is supplied by the profile of the data cell relative to the surrounding surface, and the direction of the lighting of the reading device. Light beams are sometimes recaptured, or directed in such a way to cast xe2x80x98shadows,xe2x80x99 or are directed to reflect away from the reading device. Three dimensional bar code readers are known in the art, and include the readers formerly manufactured by the Sensis Corporation (laser illuminated), and more readily available optical readers manufactured by such companies as Cognex Corporation, DVT, Inc., Robotic Vision Systems, Inc., and others. Most of the reading systems now capable of deciphering three dimensional, or Bumpy, bar codes evolved out of vision inspection systems, and have made their appearance in the marketplace relatively recently.
Three dimensional bar codes have proved to be a much better choice in some situations as they will not easily rub off, smear, peel, or vanish because bonding strengths, in essence, equate to a direct part marking system, or in case of molding processes, are, in fact, simply contours in the part itself.
Three-dimensional bar codes can be painted over or the article on which they are placed can be subjected to various treatment processes without the readability of the bar code being adversely affected. Three-dimensional bar codes are also useful where a traditional printed bar code label will not adhere to the surface of the article to be labeled.
The use of bar codes during manufacture for work-in-process tracking, inventory control, work piece routing, etc., has become a valuable tool. Embedding, or molding, the bar code into the article during its manufacture is the most expedient and cost effective identification system. However, due to the harsh environments in which many manufacturing processes occur embedding or molding a bar code into a manufactured article can present many challenges. These challenges involve overcoming the ill effects caused by the very high temperatures, abrasive and corrosive treatments and processes, and pressures that are present in, e.g., cast and molding processes, forging, machining, and other manufacturing or remanufacturing processes. In addition to OEM manufacturing there are millions and millions of parts, often safety critical, that are currently in use which need traceability, and in some instances, require traceability by reason of governmental regulation. Thus, there is a need in the art for a bar code stencil which can be easily and reliably used for embedding, molding, or otherwise adhering bar codes by means of a direct part marking process into or onto articles during their manufacture, remanufacture, maintenance, or normal use.
Accordingly, it is an objective of the present invention to obviate the above-noted shortcomings and disadvantages of present methods of marking an article with a bar code.
It is a further objective of the present invention to provide an improved method of bar code marking which is more reliable and cost effective than conventional methods.
It is a still further objective of the present invention to provide an improved method of bar code marking which is economical to implement and simple in operation.
It is a still further objective of the present invention to provide an improved method of bar code marking which can be used in harsh environments.
It is another objective of the present invention to provide an improved method of bar code marking which can be used to embed a bar code into a metal cast article during the casting process.
It is a further objective of the present invention to provide an improved method of bar code marking which can be used to embed a bar code into a molded article, of whatever material made, during the molding process.
It is a another objective of the present invention to provide an improved method of bar code marking which can be used to bar code an article in the field, or during a maintenance, rebuilding, or revitalization process by means of chemical or mechanical bonding including, but not limited to epoxies, electrode or chemical etch processes, and thermal sprays.
It is still another objective of the present invention to provide a bar code stencil which allows all of the above noted objectives to achieved.
The bar code stencil of the present invention, allows the embedding of a permanently formed bar code into a cast metal or molded part at the point of manufacture. The stencils can have sequentially numbered bar codes that are placed directly into a mold cavity. Once in the cavity, the mold is closed and filled as normal with the desired material. The result is a bar code that is literally molded or cast onto or into the surface of the finished article out of the same material as the article.
In thermal spray application of bar codes, the bar code stencil of the present invention allows the embedding and/or bonding of a permanently formed bar code onto and/or into a part by means of extremely high temperatures and mechanical bonding of selected materials into the part being marked. Thermal spray processes are well established and used in many industries. Thermal spray processes were invented nearly a hundred years ago, and have been extensively used in industry for nearly seventy years. Just as the bar code stencil of the present invention allows a normal casting or molding process to become a highly durable and dependable direct part marking process, so the bar code stencil of the present invention allows this immensely durable coating technology to be used as an immensely durable direct part marking process for the application of bar code symbologies. In thermal spraying, metal wires, metal powders, ceramics, or other materials are melted at a combustion point and then sprayed onto a prepared surface by means of compressed air. While the combustion point will be thousands of degrees, the surface of the part being sprayed will rarely exceed 350 degrees during the spraying process, well below temperatures that would adversely affect the structural integrity of the material out of which the part is made. As the hot, molten spray hits the part surface the disparity of the temperatures and the force of the spray causes a mechanical bond, which will be many thousands of pounds per square inch. Using this system with the present invention creates a highly durable and dependable bar code. Electrode coating and chemical etch processes can be similarly adapted to become marking systems through the use of the stencil of the present invention.
The bars which form the bar code take on a raised, three-dimensional form that has all the strength and visual characteristics of the parent article material and can be read through grease and grim unlike the bars on a printed label.
Several variations of the stencil can be provided for different article manufacturing, remanufacturing, or maintenance processes. Variations in the stencils are primarily based on the temperature and pressures that a particular process requires when generating an article. For example, casting a bar code into the side of an iron engine block requires a stencil capable of withstanding in excess of 3,000 degrees F. with very little pressure. A stencil for use in molding a bar code integral to an injection-molded article, however, requires a material capable of 5,000 degrees F and 3,500 PSI.
The stencil of the present invention can be sequentially, or uniquely, encoded with any number of digits in any x-dimension and with most of the bar code symbologies in use today, including the so-called 2D codes such as data matrix.